Before a disaster (for example, tsunami or flood) happens, if we can know a position of all the people, a notification and protection related to the disaster will be much more efficient. For example, if we can know the position of all people before the disaster occurs, we can change emergency lever for notification and protection in accordance with position information. For example, if there are no people in an area affected by the disaster, there is no need for notification and protection.
Alternatively, when such a disaster as fire, exposition explosion and earthquake happens, if we can know the position of all the people at the first time, a rescue or search will be much more efficient. For example, the position information may help making immediate rescue plan or may avoid an unnecessary search. Thus, the position information is important for anti-disaster.
In an anti-disaster field, there are equipment (instruments). For example, position equipment for fireman is used. We can know a position of fireman by using a wireless device which is mounted on the fireman. Alternatively, life detector instrument is used to detect human heat, sound, pulse, etc. We can know the position of the survivor by using this instrument.
However, there are demerits of those equipment (instruments). For example, regarding the position equipment for fireman, we can know only the position of fireman and cannot know the position of the survivor. Alternatively, regarding life detector instrument, because the accuracy for detection is sensitive to an environment, the detection range is limited.
There are prior arts determining the position of a mobile terminal. Patent literatures (PTLs) 1 and 2 disclose a wireless network system such as a cellar system used for determining position of the mobile terminal. Further, in Patent literatures 3 to 6, various technologies related to mobile communication are disclosed.
In addition, Patent Literature 7 discloses a position estimation method using RSS (Received Signal Strength) data obtained from a plurality of base stations. In this method, distances between the base stations and terminal are estimated based on the RSS data.
[PTL 1]
WO1997/014257A1
[PTL 2]
WO2002/052873A1
[PTL 3]
European patent Application Publication No. EP1353524A1
[PTL 4]
United States Patent Application Publication No. US2012-0231727A1
[PTL 5]
United States Patent Application Publication No. US2002-0183069A1
[PTL 6]
United States Patent Application Publication No. US2014-0302877A1
[PTL 7]
Japanese Patent Laid-open Publication No. JP 2011-215001A